Cross-leg Pedicled Free Scapular Flap for the Repair of Extensive Soft Tissue Defect with Tibial Bone Exposure

The “gold standard” for coverage of severe lower extremity injuries is free tissue transplantation. Free scapular flaps, such as free fasciocutaneous flaps, are suitable for many lower extremity applications and often provide excellent contour reproduction and appearance.¹ The blood circulation in the free scapular flap must be reestablished by anastomosing its pedicle to recipient vessels. In other words, there must be vessels available for anastomosis. Unfortunately, injury to a lower extremity is sometimes very serious, complicated, and prone to infection resulting in damage to recipient vessels and vascular obstruction, so there may not be vessels to be anastomosed in the recipient site. In this situation, the vessels of the contralateral lower extremity can provide temporary blood supply while neovascularization between the bed and the flap occurs. This technique was called the cross-leg pedicled free flap and has been performed for several years.^2,3 This study extends the indications and reports successful use of the cross-leg pedicled free scapular flap to cover an extensive soft tissue defect with tibial bone exposure of the lower leg in 13 patients. Good results were obtained and the cross-leg pedicled free scapular flap appears to be suitable for these wounds.

Methods

The study included 13 patients from May 2000 to October 2005. There were 11 men and 2 women. Ages ranged from 18 to 52 years with a mean age of 35 years. All patients had extensive soft tissue defects of the lower leg with tibial bone exposure and variable wound infection (Figure 1). The defects ranged in size from 8 cm x 15 cm to 15 cm x 30 cm. Wounds were caused by accident (6 patients), burn (2 patients), electrical injury (3 patients), and fall (2 patients). The soft tissue defects were so severe that there were no suitable vessels to be anastomosed in the recipient sites. All patients were treated with free scapular flaps to cover the defects and the vessels of the free scapular flaps were anastomosed with the dorsalis pedis vessels of contralateral leg in order to provide temporary blood supply.
Operative technique. The vessels of the recipient site were evaluated after wide radical debridement of all necrotic or infected tissue. If there was no suitable vessel to use, a cross-leg pedicled scapular flap was performed. The scapular flap was marked according to the defect so that the area of the scapular flap was a little larger than the defect in order to form the pedicle and cover the extensive soft tissue defect with no tension. The area of the scapular flap was from 10 cm x 15 cm to 15 cm x 35 cm (Figure 2). Dissection of the scapular flap was carried out in a routine manner (Figure 3). The local flap of the dorsum pedis was then lifted up to the contralateral limb and the dorsalis pedis vessels were dissected. The free scapular flap was transferred to cover the defect and its vessels were anastomosed with the dorsalis pedis vessels. The local flap was turned over and sutured with the pedicle part of the free scapular flap to form the skin pedicle (Figure 4). The 2 legs were in a cross-position and the knee of the donor limb was in flexion, which was fixed by plaster cast. Typically, the pedicle was divided after 4 to 5 weeks. The local flap was re-sutured and the pedicle part of the scapular flap was used to repair the secondary defect or was resected.

Results

The blood supply was re-established in all 13 patients. All free scapular flaps survived and the defects were covered completely (Figure 5). The defective lower extremities had regained function and there were no deformities in donor sites of the contralateral lower leg.

Discussion

An extensive soft tissue defect of the lower leg is difficult to treat and always prone to infection.⁴ There is not enough local flap to cover the defect and the skin graft is usually unsuitable. Prior to the advent of reconstructive microsurgery, patients with these problems required multistage operative procedures or amputation of the extremity. Today, free tissue transfers have been particularly useful in reconstruction of the lower leg. The most common applications have been soft tissue coverage of the tibia and (when combined with the lateral border of the scapula as an osteocutaneous graft) replacement of large bone defects of the leg. The free scapular flap, as one of the free fasciocutaneous flaps, is suitable for this situation and often provides excellent contour reconstruction and appearance.¹
In the early days of reconstructive microsurgery, free tissue transfers to the lower extremity had the highest incidence of flap failure of any area of the body.⁵ This problem has been partially solved by an appreciation of the importance of using undamaged vessels and by the use of new surgical techniques. However, nearly all subacute and chronic tissue defects of the lower leg are surrounded by a zone of tissue that has undergone an inflammatory and healing response. Vessels that are within this zone of injury, even when the healing response appears quiescent, are prone to develop spasm when dissected or divided. Vessels within this region do not have the normal pristine appearance of an artery and vein but are fixed in place by a thin layer of fibrous tissue and appear slightly more rigid than normal. When these arteries are divided the vessels retract and spasm. The vessels will have a less than normal spurt of blood and, over a few minutes, the spurt will change to a dribble. Anastomoses to this vessel will always thrombose because of the low flow rate.⁵ When a soft tissue defect of the lower leg is so extensive that the adjacent vessels are unsuitable or unavailable for microanastomosis, it is important to select a suitable donor site to offer blood supply. Carrier vessels from distant donor sites can nourish the flap temporarily while neovascularization occurs between the bed and the flap. This concept of a “free-flap carrier” was described by Taylor et al.² Since then, muscle or fasciocutaneous free flaps were successfully transferred into remote carrier vessels to cover complex defects after trauma, burn, or cancer resection.^6,7 According to this concept, free flaps pedicled on the contralateral leg may be safer in such cases. The present study extended the indications and reported successful experiences using the cross-leg pedicled free scapular flap to cover the extensive soft tissue defect with tibial bone exposure of the lower leg in 13 patients. Good results were obtained and the advantages are obvious.
The free scapular flap was developed by dos Santos⁸ and clinically applied by Gilbert.⁹ It has been used successfully for reconstruction of various defects in the head, neck, and upper and lower extremities. The attractiveness of this flap is based on the constant vascular anatomy of the circumflex scapular artery, the long vascular pedicle, and the ability to close the donor site directly.¹⁰ In the present series, the vascular pedicle of the free scapular flap was 14 cm long, which is adequate to reach the contralateral leg facilitating microanastomosis and avoiding excessive dissection of the dorsalis pedis vessels. The vessel donor site of the contralateral foot will also experience less deformity.
The free scapular flap, supplied by a single circumflex scapular vascular pedicle, can be safely harvested beyond the midline of the back. The upper back can be a donor for very large and long flaps, ideal for resurfacing large defects.¹⁰ The largest flap was 39 cm x 15 cm, which can cover the extensive soft tissue defect with no tension and facilitates skin pedicle formation with the local flap of the contralateral foot. The infected, devitalized tissues and poorly vascularized scar tissue can be resected completely helping prevent infection from reoccurring. It is particularly advantageous in patients requiring a large surface area of soft tissue to restore their defect.¹¹
The free scapular flap is thinner than the myocutaneous flap and is suitable for the lower leg, especially for the anterior part of the tibia. The appearance of the healed leg is quite acceptable, with good contour, color match, and durable coverage. The contour is not as clumsy as the free myocutaneous flap and the flap is easy to thin after 6 months.
Regarding the bone defect, Donski et al¹² has reported that the free scapular flap can be used with the lateral border of the scapula as a reliable osteocutaneous flap. Reconstruction with vascularized free bone transfer provides immediate structural support, is rapidly incorporated, and is able to form new bone without bone resorption.¹³ The osteocutaneous scapular free flap, which permits the patient rapid rehabilitation of the lower leg, is thought to be a good choice because it allows the patient to get out of bed as quickly as possible in the postoperative period to minimize additional complications.¹⁴ Although the free scapular osteocutaneous flap was not used in this series, the advantage of the free scapular osteocutaneous flap is manifested and has been reported.¹⁵
For free tissue transfers to the lower leg, it is preferable to do the anastomoses near the ankle because the vessels are superficially located and more accessible. Therefore, the authors used the dorsalis pedis vessels to anastomose with the free scapular flap in all of the patients because it is easy to dissect and anastomose. After dividing the skin pedicle, the local flap was re-sutured. The donor site showed no morbidity and the function of the foot was normal.

Conclusion

Use of the cross-leg pedicled free scapular flap in patients with a difficult wound of the lower extremity with extensive tissue defect and tibial bone exposure is a worthwhile procedure and should be attempted if possible. The scapular flap has several advantages applicable to the cross-leg pedicled free flap technique. Although the operation is divided into 2 stages, it solves the problem and can offer temporary blood supply when there is no vessel for anastomosis in the recipient site, which decreases the risk of microanastomosis and produces good results.